And in a lot of cases, they actually take on some of the big personality traits from their owners.

The researchers found that people who are outgoing had dogs that were more active and excitable . . . people who are unhappy had dogs that were more fearful and harder to train . . . and agreeable people had dogs that were less aggressive.

The results were a surprise to the researchers, who say, quote, "We expected the dogs' personalities to be fairly stable because they don't have wild lifestyle changes [like] humans do, but they actually change a lot."

“When humans go through big changes in life, their personality traits can change. We found that this also happens with dogs – and to a surprisingly large degree,” explains lead author William Chopik, professor of psychology at MSU, in a university release. “We uncovered similarities to their owners, the optimal time for training and even a time in their lives that they can get more aggressive toward other animals.”